This is the first application filed for the present invention.
The present application relates to an optical interferometer, and in particular to a bulk optical interferometer based on a Mach-Zehnder interferometer (MZI) for use as a wavelength channel interleaver/de-interleaver.
Optical interleavers are becoming a popular tool in dense wavelength division multiplexed (DWDM) communications networks as an interface between components designed for signals with a first wavelength channel spacing and components designed for signals with a second wavelength channel spacing. In the past 200 GHz channel spacing was the norm, but as the demand for increased bandwidth grew, 100 GHz channel spacing became the standard. In the next generation of communications networks 50 GHz channels spacing and even 25 GHz channel spacing will become common place. However, conventional de-multiplexing filters, e.g. dichroic filters, do not have the capability to separate channels that are so closely spaced without complex and expensive modifications, and without resulting in significant channel crosstalk. Accordingly, optical interleavers are used to separate the closely spaced channels into two sets of channels, which are twice as far apart. This process can continue until the channels are far enough apart for conventional multiplexing to be effective.
Interleavers have taken several different forms including: Birefringent Crystal Interleavers (BCI) such as the one disclosed in U.S. Pat. No. 6,301,046 issued Oct. 9, 2001 in the name of Kuochou Tai et al; Integrated Lattice Filter Interleavers such as the one disclosed in U.S. Pat. No. 5,596,661 issued Jan. 21, 1997 in the name of Charles Henry; and Michelson Gires-Tournois Interleavers (MGTI) such as the ones disclosed in U.S. Pat. No. 6,304,689 issued Oct. 16, 2001 in the name of Benjamin Dingel et al., U.S. Pat. No. 6,252,716 issued Jun. 26, 2001 in the name of Reza Paiam, and U.S. Pat. No. 6,169,828 issued Jan. 2, 2001 in the name of Simon Cao. A polarization based interleaver using a split-mirror ring resonator is disclosed in U.S. Pat. No. 6,243,200 issued Jun. 5, 2001 in the name of Gan Zhou et al.
An object of the present invention is to overcome the shortcomings of the prior art and provide a simple bulk optical interleaver with very few parts that is easily manufactured at low cost and provides reliable and stable performance.
Accordingly, the present invention relates to an optical interferometer device comprising:
a first input port for launching an input optical beam;
a first beam-splitter for separating the input optical beam into first and second sub-beams traveling along first and second paths, respectively;
a first ring resonator positioned in the first path including at least two substantially fully reflective surfaces and a first partially reflective surface, the first partially reflective surface for passing a portion of the first sub-beam into the first ring resonator, while reflecting the remainder of the first sub-beam away therefrom, whereby light exiting the first ring resonator is combined with the remainder of the first sub-beam forming a first recombined sub-beam;
a second ring resonator positioned in the second path including at least two substantially fully reflective surfaces and a second partially reflective surface, the second partially reflective surface for passing a portion of the second sub-beam into the second ring resonator, while reflecting the remainder of the second sub-beam away therefrom, whereby light exiting the second ring resonator is combined with the remainder of the second sub-beam forming a second recombined sub-beam;
a second beam splitter for receiving the first and second recombined sub-beams resulting in the interference thereof and the production of a first output beam and a second output beam;
a first output port for outputting the first output beam; and
a second output port for outputting the second output beam.
Another aspect of the present invention relates to a Mach-Zehnder interferometer comprising:
a beam splitter for separating an input beam of light into a first sub-beam and a second sub-beam, and for directing the first and second sub-beams along first and second arms, respectively, of the interferometer;
a first ring resonator in the first arm of the interferometer having a first resonator delay for effecting the phase response of the first sub-beam;
a second ring resonator in the second arm of the interferometer having a second resonator delay for effecting the phase response of the second sub-beam;
a beam combiner/splitter for interfering the first and second sub-beams resulting in first and second output beams.